Nutricia North America Phlexy-10 System Supplements Drink Mix 20g Packet, 69 Calories, Blackcurrent/Apple, Phenylalanine-free Nutricia Phlexy 10 System Supplements is an interchangeable system of phenylalanine-free medical foods for the dietary management of phenylketonuria (PKU) in children of one year and older and adults, including pregnant women and women of child bearing age.